Supercritical Water Oxidation of Coal Gasification Wastewater

The sludge produced by biochemical treatment process of coal gasification wastewater contains large amount of phenol and tar, it is difficult to be degraded by conventional methods. Supercritical water oxidation (SCWO) technique was carried out for biochemical sludge from coal gasification wastewater treatment. The effect of temperature, pressure, oxidation ratio and reaction time was studied and the operation parameters were optimized. Results showed that higher temperature and oxidation ratio, longer reaction time effectively promoted the pollutants removal, while the effect of pressure was little. For a biochemical sludge with moisture content of 88%, the COD and NH3-N in effluent were 42 and 5 mg/L, respectively and the concentration of volatile phenol was below the limit of detection when treated at 873K, 25MPa, oxidation ratio of 3.5 and reaction time of 60s. The effluent quality can reach the national wastewater discharge standard I of GB 8978-1996. The study provided a new idea for the treatment of refractory sludge containing high concentration of tar and phenol.